Method of controlling a treatment line

ABSTRACT

The invention relates to a method of controlling a treatment line. According to said method a) a correlation between one or several variable parameters of the chemical and/or physical processes of the treatment line and one or several characteristic values that are characteristic of the success of the treatment is established; rules are derived of this correlation that describe the dependence of the characteristic value or the characteristic values of the variable parameters; the correlation and/or the rules derived therefrom are stored in a control system for the treatment line; b) the one or the several characteristic value(s) is/are measured continuously or discontinuously; c) if said characteristic values deviate from a predetermined standard range of values, the/those variable parameter(s) that is/are most closely correlated with said characteristic value is/are modified in the direction which counteracts the deviation of the characteristic value or the characteristic values from the standard range.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage application filed under 35U.S.C. §371, claiming priority under 35 U.S.C. §§119 and 365 ofInternational Application No. PCT/EP99/07527, filed Oct. 7, 1999, in theEuropean Patent Office and DE 198 57 799.0, filed on Dec. 15, 1998, inthe German Patent Office.

This invention relates to a process for controlling a treatment line, inwhich a workpiece is treated by chemical and/or physical processes. Moreparticularly, the invention relates to processes in which the surface ofthe workpiece is chemically modified and/or coated. An example of suchan application is the phosphating and the subsequent painting of metals,more particularly car bodies.

There are a large number of industrial processes in which a workpiece istreated by chemical and/or physical treatment processes. One objectiveof such treatment may be the chemical modification of the surface of theworkpiece or its coating, for example its paint. A frequent objective ofsuch processes is to give desired technical or aesthetic properties tothe surfaces of the workpieces. One example of this are processes bywhich the surface of the workpieces may be protected from corrosion orby which the surface of the workpiece is given a desired, aestheticallyattractive appearance.

In all these cases, the aim of treating the workpieces by chemicaland/or physical processes is to produce certain technical or aestheticeffects. Whether the desired result is achieved depends on the substrateand on the selected parameters of the chemical and/or physicalprocesses. The more precisely it is known which of the selectableparameters influence the desired result and how they do so, theparameters may be so adjusted that the desired result is achieved asreliably as possible or that the intended technical and/or aestheticresults of the treatment are as good as possible. In this connection,various constants which are considered to be characteristic of theintended result are defined. These constants correlate in different wayswith one or more of the parameters of the chemical and/or physicalprocesses by which the desired result is to be achieved. The practicalknowledge of which parameters of the chemical and/or physical processesinfluence the result and in what way they do so is mostly of anempirical nature and has been acquired and improved in series of tests.Nevertheless, it is by no means guaranteed that all correlations betweenthe parameters of the chemical and/or physical processes and the resultsattained by the treatment are now known sufficiently well and that theseparameters are so adjusted that the desired result is achieved asoptimally as possible. Accordingly, there is a need to refine the knowncorrelations and to find new correlations. There is also a need, in theevent of deviations of the obtained result from the intended result, torecognize those parameters of the chemical and/or physical processes andto be able to vary them in such a way that deviations of the obtainedresult from the intended result may be corrected as reliably aspossible.

DESCRIPTION OF THE INVENTION

The present invention relates to a process for controlling a treatmentline, in which a workpiece is treated by chemical and/or physicalprocesses, characterized in that:

a) a correlation between one or more variable parameters of the chemicaland/or physical processes of the treatment line and one or moreconstants which are characteristic of the outcome of the treatment isestablished, from it rules are derived which define the dependence ofthe constant or of the constants on the variable parameters and thecorrelation and/or the rules derived from it are stored in a controlsystem for the treatment line;

b) the one or more constants characteristic of the outcome of thetreatment are measured continuously or intermittently; and

c) in the event of a deviation of these constants from a given range ofset values or in the event of a significant tendency of these constantsto move towards the limits of the range of set values, that/thosevariable parameter(s) of the chemical and/or physical processes of thetreatment line which is/are most closely correlated with this constantis/are altered in accordance with the correlation established in step a)and/or the rules derived from it in that direction which counteracts thedeviation of the constant or constants from the range of set values.

In this connection, it is of course advisable to alter only thoseparameters of the chemical and/or physical processes of the treatmentline which do not adversely affect the other constants that arecharacteristic of the result. The chosen parameters of the chemicaland/or physical processes are therefore those whose alteration iscorrelated as closely as possible with the diverging constant and whosealteration does not have a negative effect on other constants. This maybe effected, for example, by a computer programme operating on the linesof an expert system.

The process according to the present invention is preferably carried outin such a way that, in step c), the alteration of the variableparameters of the chemical and/or physical processes of the treatmentline takes place automatically without human intervention or that thecontrol system for the process issues an appropriate recommendation toalter the variable parameters. The first alternative corresponds tofully automatic operation of the treatment line; in the secondalternative, the operating personnel receive precise information as towhich parameters are to be altered and in what way as the outcome of theprocess according to the invention.

The control system for the process according to the present invention ispreferably installed so that it is “adaptive”. Accordingly, the processaccording to the present invention is preferably started in such a waythat, during the operation of the treatment line, the correlationbetween the variable parameters of the chemical and/or physicalprocesses of the treatment line and one or more constants characteristicof the outcome of the treatment, and/or the rules derived from it, areadapted. Care is accordingly taken to ensure, firstly, that the controlsystem receives—continuously or at specific times—information about thevalues of as many as possible of the parameters of the chemical and/orphysical processes of the treatment line. This may be effected, forexample, by automatically analyzing chemical processing liquids usedduring the treatment of the workpieces and passing the results of theanalyses to the control system for the process according to theinvention. This may of course also be done by manual input. Secondly,care is taken to ensure that the control system is informed as fully aspossible about the outcome of the chemical and/or physical treatment,i.e. that it receives information about the values of as many aspossible of the constants which are important to the result of thetreatment. As far as possible, this is preferably also carried outautomatically, but otherwise by manual data input. In this way, thesystem is placed in the position of being able continually to improvethe correlation between the actual parameters and the results achievedand, if necessary, to find new correlations.

The manner in which the correlation between the individual variableparameters of the chemical and/or physical processes of the treatmentline and the constants characteristic of the outcome of the treatmentare stored in the control system and evaluated is basically unimportant.For example, the rules derived from the empirically discoveredcorrelation may be expressed in the form of mathematical equations, asimprecise relations (“fuzzy logic”)or in the form of model-freealgorithms, such as neuronal networks. Suitable mathematical equationare, for example, multilinear regression methods or a partial leastsquares regression.

In one particular embodiment, the process according to the presentinvention may be carried out at a plant in which chemical modificationand/or coating of the surface of the workpiece is carried out. A coatingmay consist, for example, of a single-layer or multi-layer paintstructure. The chemical nature of the workpiece is initially notrelevant. For example, a workpiece may be made of a natural substance,such as wood, of a plastic, of a ceramic material or of metal. Forexample, a plastic surface whose coating behavior is to be improved bychemical and/or physical treatment may be involved. A chemical treatmentmay consist, for example, in an oxidizing attack on the plastic surface.One example of a possible physicochemical process is a plasma treatment.Processes in which the metal surface is chemically modified may beinvolved, particularly in the case of metal workpieces. In this way,corrosion prevention may be improved and/or a desired surface appearanceobtained. Examples of such processes are anodizing, chromating, atreatment using complex fluorides, optionally in combination withorganic polymers, an alkaline passivation or layer-forming ornon-layer-forming phosphating. After such a chemical modification, themetal surface may in addition be coated, for example by painting orenamelling. Depending on the type of metal and on the chemicaltreatment, an additional coating may be unnecessary. In one example ofembodiment of the process according to the invention, the treatment lineis a phosphating plant for the phosphating of metal surfaces beforepainting. In this application, phosphating is preferably carried out asso-called layer-forming phosphating in the form of zinc phosphating. Inthe course of this, a layer only a few μm in thickness consisting ofcrystalline zinc phosphate or of phosphates in which metals other thanzinc (iron, nickel, manganese . . . ) are incorporated as cations isformed on the metal surface. Such phosphating processes are used, forexample, in the metal industry, in vehicle manufacture and in the whitegoods industry.

In industrial plants of the type used, for example, in car production,the phosphating plant as a whole, besides having one or more phosphatingzones, generally includes one or more cleaning zones and apre-phosphating activation zone and, frequently, a post-passivation zoneafter phosphating. As a rule, intermediate rinsing with water is carriedout between the individual treatment steps in the different treatmentzones. Post-passivation in the post-passivation zone, which in favorablecases may even be dispensed with, is generally followed by painting. Incar manufacture, the first painting step is normally cathodicelectrophoretic coating. However, anodic electrophoretic coating mayalso be used or the first paint layer may be applied, without theassistance of current, by dipping the workpiece into the paint bath orby spray-application of the paint.

For example, layer-forming phosphating may be carried out in thephosphating zone by contacting the metal surface with an acidic aqueousphosphating solution containing 0.3 to 3 g/l zinc ions and 3 to 30 g/lphosphate ions. In the case of the acidic phosphating solutions having apH in the range from about 2.8 to about 3.8, the phosphate ions arelargely present as free phosphoric acid and as dihydrogen phosphateions.

The zinc contents in the phosphating solution are preferably in therange from 0.4 to 2 g/l and in particular 0.5 to 1.5 g/l which is normalfor low-zinc processes. The weight ratio of phosphate ions to zinc ionsin the phosphating baths may vary within wide limits, providing it is inthe range from 3.7 to 30. A weight ratio of 10 to 20 is particularlypreferred.

In addition to the zinc ions and phosphate ions, the phosphating bathmay contain other components of the type presently typical ofphosphating baths.

It is preferable to use phosphate solutions containing additional mono-or di-valent metal ions which have been found from experience to have afavorable effect on paint adhesion and on the protection of thephosphate layers thus produced against corrosion. Accordingly, thephosphating solution preferably also contains one or more of thefollowing cations:

0.1 to 4 g/l manganese(II),

0.1 to 2.5 g/l nickel(II),

0.2 to 2.5 g/l magnesium(II),

0.2 to 2.5 g/l calcium(II),

0.002 to 0.2 g/l copper(II),

0.1 to 2 g/l cobalt(II).

For example, in addition to zinc ions, the phosphate solution contains0.1 to 4 g/l manganese ions and 0.002 to 2 g/l copper ions and not morethan 0.05 g/l and in particular not more than 0.001 g/l nickel ions asadditional cations. However, if it is intended to keep to conventionaltrication technology, phosphating baths which, besides zinc ions,contain 0.1 to 4 g/l manganese ions and in addition 0.1 to 2.5 g/lnickel ions may be used.

Besides the layer-forming divalent cations, phosphating baths generallyalso contain sodium ions, potassium ions and/or ammonium ions to adjustthe free acid.

In the case of phosphating baths which are intended to be suitable fordifferent substrates, it has become common practice to add free and/orcomplexed fluoride in quantities of up to 2.5 g/l total fluoride, ofwhich up to 800 mg/l is free fluoride. In the absence of fluoride, thealuminium content of the bath should not exceed 3 mg/l. In the presenceof fluoride, higher Al contents are tolerated through complexingproviding the concentration of the non-complexed Al does not exceed 3mg/l. The use of fluoride-containing baths is therefore advantageouswhen the surfaces to be phosphated consist at least partly of aluminiumor contain aluminium. In such cases, it is favorable not to usecomplexed fluoride, but only free fluoride, preferably in concentrationsof 0.5 to 1.0 g/l.

For the phosphating of zinc surfaces, it is not absolutely essential forthe phosphating baths to contain so-called accelerators. For thephosphating of steel surfaces, however, the phosphating solution mustcontain one or more accelerators. Such accelerators are common in theprior art as components of zinc phosphating baths. Accelerators aresubstances which chemically bind the hydrogen formed as a result of theattack by the acid on the metal surface by being reduced themselves.Oxidizing accelerators also have the effect of oxidizing the iron(II)ions released by the attack on steel surfaces to the trivalent stage, sothat they may precipitate as iron(III) phosphate. Examples of suitableaccelerators are:

0.2 to 2 g/l m-nitrobenzene sulfonate ions,

0.1 to 10 g/l hydroxylamine in free or bound form,

0.05 to 2 g/l m-nitrobenzoate ions,

0.05 to 2 g/l p-nitrophenol,

1 to 70 mg/l hydrogen peroxide in free or bound form,

0.01 to 0.2 g/l nitrite ions,

0.05 to 4 g/l organic N-oxides,

0.1 to 3 g/l nitroguanidine.

In addition, nitrate ions in quantities of up to 10 g/l may be presentas co-accelerators which can have a favorable effect, particularly inthe phosphating of steel surfaces. In the phosphating of zinc-coatedsteel, *however, the phosphating solution preferably contains as littlenitrate as possible. Nitrate concentrations of 0.5 g/l should preferablynot be exceeded because, at higher nitrate concentrations, there is adanger of so-called “pinholing”, i.e. the formation of white,crater-like voids in the phosphate layer.

Particularly preferred accelerators are hydrogen peroxide—from theperspective of environmental acceptability—and hydroxylamine—for thetechnical reasons of easier formulation of regenerating solutions.However, the use of these two accelerators together is not advisablebecause hydroxylamine is decomposed by hydrogen peroxide. If hydrogenperoxide in free or bound form is used as accelerator, concentrations offrom 0.005 to 0.02 g/l of hydrogen peroxide are particularly preferred.The hydrogen peroxide may be added as such to the phosphating solution.However, hydrogen peroxide may also be added in bound form as compoundswhich yield hydrogen peroxide as a result of hydrolysis reactions in thephosphating bath. Examples of such compounds are persalts, such asperborates, percarbonates, peroxosulfates or peroxodisulfates. Othersuitable sources of hydrogen peroxide are ionic peroxides, such asalkali metal peroxides.

Hydroxylamine may be used as the free base, as a hydroxylamine complexor in the form of hydroxylammonium salts. If free hydroxylamine is addedto the phosphating bath or to a phosphating bath concentrate, it will bepresent largely as hydroxylammonium cation owing to the acidic characterof these solutions. If it is used as hydroxylammonium salt, the sulfatesand the phosphates are particularly suitable. In the case of thephosphates, the acid salts are preferred by virtue of their bettersolubility. Hydroxylamine or compounds thereof are added to thephosphating bath in such quantities that the calculated concentration ofthe free hydroxylamine is between 0.1 and 10 g/l, preferably between 0.2and 6 g/l and more preferably between 0.3 and 2 g/l.

The effect of hydroxylamine as an accelerator may be assisted by theadditional use of chlorate.

Other suitable accelerators are the organic N-oxides described in detailin German patent application DE-A-197 33 978.6. N-methylmorpholineN-oxide is a particularly preferred organic N-oxide. The N-oxides arepreferably used in combination with co-accelerators, such as chlorate,hydrogen peroxide, m-nitrobenzene sulfonate or nitroguanidine.Nitroguanidine may also be used as sole accelerator, as described, forexample, in DE-A-196 34 685.

Other parameters known to the expert for the control of phosphatingbaths are the pH and/or the free acid content and total acid content,generally expressed as a point count. The free acid point count meansthe consumption in ml of 0.1 N sodium hydroxide solution in order totitrate 10 ml of bath solution to a pH of 3.6. Similarly, the total acidpoint count indicates the consumption in ml to a pH of 8.2. Free acidvalues of between 0 and 1.5 points and total acid values of betweenabout 15 and about 30 points are within the usual technical range.

Phosphating may be carried out by dipping, spraying or spray/dipprocesses. The contact times are in the usual range of between about 1and about 4 minutes. The temperature of the phosphating solution is inthe range from about 35 to about 70° C. and more particularly in therange from about 40 to about 60° C.

Accordingly, a large number of physical and chemical parameters may beselected to determine the outcome of phosphating and the protectiveeffect of the paint subsequently applied. Physical parameters are inparticular the temperature of the phosphating bath and the phosphatingtime. It is also important whether the parts to be phosphated are dippedin the phosphating solution or sprayed with the phosphating solution orwhether the two processes are carried out one after the other in varyingorder. The adjustable chemical parameters are the composition of thephosphating solution and the free acid content and total acid content.Accordingly, the variable parameter or parameters may be selected fromthe temperature of the phosphating solution, the zinc concentration inthe phosphating solution, the free acid content or total acid content inthe phosphating solution, the concentration of one or more acceleratorsin the phosphating solution, the concentration of polyvalent metal ionsother than zinc in the phosphating solution, the period for which themetal surface is in contact with the phosphating solution and themovement of the phosphating solution relative to the metal surface (bathagitation, spray or dip processes, spraying pressure).

However, the outcome of phosphating, expressed in constants, does notdepend solely on the composition of the phosphating bath or on thephysical phosphating parameters, but also on previous or subsequenttreatment steps. For example, the composition of a pre-phosphatingcleaning bath may be of significance to the outcome of phosphating. Thesame applies to the activating bath by which, as a rule, phosphating isimmediately preceded. Equally, treatment with a post-passivation bathafter phosphating and before painting may be of significance toconstants, such as paint adhesion and corrosion resistance.

Pre-phosphating cleaning baths normally contain anionic and/or non-ionicsurfactants together with alkaline builders in aqueous solution.Activating baths generally contain colloidal titanium phosphates in anaqueous solution of disodium hydrogen phosphate having a pH in the rangefrom about 8 to about 9. Post-passivation baths based on chromates orchromic acid, on reactive polymers, such as amino-substitutedpolyvinylphenol derivatives, and on complex titanium fluorides and/orzirconium fluorides are known as are copper-containing post-passivationbaths. The effect of these baths in connection with phosphating dependson their composition, the temperature, the treatment time and the typeof treatment (spraying or dipping). Where there are intermediate rinsingsteps, especially during the final rinse before cathodic dip coating,the purity of the final rinse water, expressed by its electricalconductivity, may also be of significance. In the process according tothe invention, the correlation of these parameters with the constantscharacteristic of the outcome of the treatment may be determined andused for the control of these treatment steps. Accordingly oneembodiment of the process according to the invention involves selectingthe variable parameter or parameters from the temperature and/orcomposition of one or more cleaning baths before the phosphating zone,of an activating bath before the phosphating zone and/or of apost-passivation bath after the phosphating zone and/or the period forwhich these baths are in contact with the metal surface.

For the selected example of phosphating, there are a number of constantsthat are characteristic of the outcome of the treatment. The constantsmay be selected, for example, from the layer weight of the phosphatelayer, the chemical composition of the phosphate layer, the current flowthrough the phosphate layer during cathodic polarisation, the thicknessof an electrophoretic coating applied after phosphating, the adhesion ofa paint applied after phosphating, the surface structure (roughness,undulation, gloss etc.) of a paint applied after phosphating and thesusceptibility of the workpiece to corrosion after phosphating andpainting.

Various methods are available for the measurement of these constants.The easiest way of determining layer weight is to detach the phosphatelayer and to weigh a sample metal plate before and afterwards. The layerweight may be determined non-destructively, for example by infraredspectroscopy (characteristic vibrations of the phosphate groups). Thechemical composition of the phosphate layer may be determined byconventional analysis, for example by atomic absorption spectroscopy,after its removal. After appropriate calibration, the proportion ofselected elements in the phosphate layer may also be determined by X-rayfluorescence measurement. Measurement of the current flow through thephosphate layer during cathodic polarization is a quick way ofestimating the corrosion resistance of the phosphate layer. The adhesionof a paint applied after phosphating may be determined by standardtests, such as Erichsen indentation, the T-bend test or a stone impact(chipping) test in a corrosive environment. Various corrodibility testsare available, including the salt-spray test, the alternating-climatetest and the outdoor weathering test, generally carried out using metaltest plates intentionally damaged by scoring.

If the constants cannot be determined on-line and automatically in theproduction process and passed to the control system for the process,they have to be determined separately and the results have to be fedmanually (locally or at a remote location) into the control system.

At the beginning of the process according to the invention, it is ofcourse necessary to preset starting values for the parameters of thechemical and/or physical processes. These starting values may come frompreviously determined correlations. However, it is also possible to takestarting values which are known from the prior art for the respectivetreatment process or which are known from experience. The processaccording to the invention is then used to refine these startingparameters in the course of the process in such a way that optimalvalues are obtained for the relevant constants. In this connection,certain parameters may be preset to vary only within limits to bepredetermined.

The results of the measurements of the one or more constants carried outin step b) and/or the measures taken in step c) are preferably recordedon a data carrier during the process according to the invention. Theyare then available for purposes of quality control and for checking thecorrelations with optionally other procedures than those used in theprocess according to the invention. Recording on a data carrier may takeplace locally, i.e. at the place where the process according to theinvention is carried out. However, the data may also be transmitted toor directly fed in—continuously, periodically or in response to arequest—at a remote location which may even be outside the productionplant in which the chemical and/or physical process takes place. Forexample, this remote location may be at the premises of the manufacturerof the treatment solutions used in the process according to theinvention. In this way, the manufacturer is regularly updated withinformation on the production process, for example on the values of thevariable parameters of the chemical and/or physical processes of thetreatment line, without any need for personnel to remain on site at thetreatment line. In this connection, it is also preferred to arrange forthe limiting values of the parameters, within which variations may bemade automatically during the process according to the invention, or theranges of set values obtained from the correlation in step a) to bereset locally or from a remote location.

The process according to the invention has the advantage that the valuesof the chemical and/or physical parameters of the treatment line areautomatically adapted whenever the constants under consideration change,for example following a change of substrate. Through the processaccording to the invention, the values of the parameters are regulatedin such a way that they are optimal for the respective substratepresent. Manual intervention is either not necessary at all for thispurpose or may be restricted to setting new limits for the permittedranges of values of the individual parameters within which the ranges ofset values may be adjusted by the process according to the invention.

EXAMPLE

The process according to the present invention was tested at aphosphating line of the type normally used in car manufacture. Carbodies are first cleaned in three baths, then activated, phosphated,post-passivated, primed with a cathodically depositable electrophoreticcoating and then coated with filler and painted.

The following constants were selected for the effectiveness of thistreatment chain:

1. chipping value in the VW test (K value: best value, K = 1; worstvalue, K = 10), 2. paint creepage to DIN 53167 after 10 one-week testcycles with a complete paint structure, 3. paint thickness of thecomplete paint structure, 4. CEC thickness = thickness of the cathodicelectrophoretic coating for preset electrical deposition parameters.

Variable Parameters: (Set Values in Brackets)

Cleaning Baths and Activation Bath (=“Pretreatment” Before Phosphating):

Bath 1 alkalinity of the first cleaning bath (in mol. equivalents; setvalue: 80-110) Bath 2 alkalinity of the second cleaning bath (in mol.equivalents; set value: 80-110) Bath 3 alkalinity of the third cleaningbath (in mol. equivalents; set value: 175-185) Active conductivity ofthe activation bath in μS/cm² (as a measure of cleaning solution carriedover)

Phosphating Parameters (Including Post-passivation):

T.A. total acid (23-28 points) F.A. free acid (0.7-1.1 points) Zn zincconcentration in the phosphating bath (3.0-3.7 points, corresponding to1-1.2 g/l) HAS concentration of the accelerator hydroxylammonium sulfatein the phosphating bath (2-3.5 g/l) Cr(VI) concentration in thepost-passivation bath (5.0-7.0 g/l)

Parameters of the CEC Bath (Cathodic Dip Coating):

pH pH Con conductivity in the CEC bath in μS/cm² TSC total solidscontent in wt. % (19-20) PBR pigment binder ratio (0.57) MEQmilliequivalents of acid (45-55)

Pretreatment Parameter/Target value Bath 1 Bath 2 Bath 3 Active K valueCreepage Thickness 0.6 0.03 Thickness CEC Phosphating Parameter/Targetvalue T.A. F.A. Zn HAS CrVI K value −6.4 Creepage 0.2 0.7 Thickness 59.0Thickness CEC −5.3 CEC Parameter/Target value pH Con TSC PBR MEQ K valueCreepage Thickness Thickness CEC −9.5 27.9

The correlation Table shows the correlation matrix between chemicalparameters and constants investigated in the event of variations in thevalues of the chemical parameters such as occur with time in anindustrial automotive phosphating line. The correlation was determinedby the method of multilinear regression and significance assessment by“anova” (=analysis of variance). Significant regression coefficients areshown in the Table.

Thus, the K value correlates negatively with the zinc concentration,i.e. a high zinc concentration in the phosphating bath results in thedesired lower values of the K value. By contrast, paint creepagecorrelates in particular with the values for the total acid and for theconcentration of the accelerator hydroxylamine in the phosphating bath.The total paint thickness is associated with the zinc content of thephosphating bath and otherwise correlates with the parameters Bath 3 andActive. Unlike the thickness of the total paint structure, the thicknessof the CEC layer correlates negatively with the zinc concentration inthe phosphating bath and otherwise with pH and PBR in the CEC bath.

What is claimed is:
 1. A treatment line process comprising treating aworkpiece by one or more chemical and/or physical processes, saidprocesses having one or more variable parameters and one or moreconstants, said constants defining an outcome of the treatment upon theworkpiece and having set values with limits defining a desired outcomeof the treatment, said process further comprising the steps of: a)establishing a correlation or set of correlations between one or more ofthe variable parameters of the chemical and/or physical processes of thetreatment line and the one or more constants that define the outcome ofthe treatment, deriving rules that define the correlation orcorrelations between the one or more constants and the one or morevariable parameters, and storing the correlation or correlations and/orthe rules derived from them in a control system for the treatment line;b) continuously or intermittently measuring the one or more constantsthat define the outcome of the treatment; and c) where one or more ofthe measured constants approach or deviate from the limits of theirrespective set values, altering one or more of the correlationsestablished and/or the rules derived in step a) to return or maintainthe one or more of the measured constants that are approaching ordeviating from the limits of their respective set values to or withinthe limits of their respective set values, wherein the altering of theone or more correlations and/or rules take place automatically withouthuman intervention or wherein the control system for the process issuesa recommendation to alter the one or more correlations and/or rules, andwherein the one or more correlations and/or rules are altered by one orboth of a multilinear regression or partial least squares regressionmethod.
 2. The process of claim 1, wherein the rules derived from thecorrelation or correlations between the one or more variable parametersof the chemical and/or physical processes of the treatment line and theone or more constants defining the outcome of the treatment areexpressed in the form of mathematical equations, as imprecise relations,or in model-free algorithms.
 3. The process of claim 1, wherein thetreatment of the workpiece comprises a chemical modification and/or acoating of the surface of the workpiece.
 4. The process of claim 1,wherein the treatment line is a phosphating line for the phosphating ofmetal surfaces before painting.
 5. The process of claim 4, wherein thephosphating line comprises one or more phosphating zones and one or moreof a cleaning zone, an activation zone, or a post-passivation zone. 6.The process of claim 5, wherein layer-forming phosphating is carried outin the phosphating zone by contacting the metal surface with an acidicaqueous phosphating solution containing 0.3 to 3 g/l zinc ions and 3 to30 g/l phosphate ions.
 7. The process of claim 6, wherein the variableparameter or parameters comprise one or more of phosphating solutiontemperature, zinc concentration in the phosphating solution, pH of thephosphating solution, free acid content of the phosphating solution,total acid content of the phosphating solution, concentration of one ormore accelerators in the phosphating solution, concentration ofpolyvalent metal ions other than zinc in the phosphating solution,contact time between the metal surface and the phosphating solution, andmovement of the phosphating solution relative to the metal surface. 8.The process of claim 5, wherein the variable parameter or parameters areselected from temperature and/or composition of one or more cleaningbaths before the phosphating zone, of an activation bath before thephosphating zone and/or of a post-passivation bath after the phosphatingzone and/or from contact time between any of these baths and the metalsurface.
 9. The process of claim 5, wherein the one or more constantsdefining the outcome of the treatment comprise one or more of the layerweight of the phosphate layer, the chemical composition of the phosphatelayer, the current flow through the phosphate layer during cathodicpolarisation, the thickness of an electrophoretic coating applied afterphosphating, the adhesion of a paint applied after phosphating, thesurface structure of a paint applied after phosphating, and thesusceptibility of the workpiece to corrosion after phosphating andpainting.
 10. The process of claim 1, wherein the measuring of the oneor more constants in step b) and/or the altering in step c) of the oneor more correlations established and/or the rules derived in step c) arerecorded on a data carrier.
 11. The process of claim 1, wherein thelimits of the set values of the parameters are varied or resetautomatically during the process locally or from a remote location.